River Falls, Wisconsin – A former teacher’s aide has been charged with sexual assault.

She’s been accused of having sex with a 12-year-old several times, including at a school. Not only that, the child claims the woman put a gun to his head and threatened to kill his family if he ever told anyone about their relationship.

Rebecca O’Malley-Tietz, 34, (pictured left) from River Falls, has been charged with first degree sexual assault of a child. She used to be a teacher’s aide for the Harbor Program at the River Falls Academy before being fired last year.

Police say the boy told them O’Malley-Tietz would write notes to him at school. Eventually, he told officers he started staying at her house overnight as their relationship allegedly escalated.

Police interviewed O’Malley-Tietz and claim she, at first, denied they had sex, but later changed her story. She told them they did, but that he forced himself on her.

O’Malley-Tietz was scheduled to make her first court appearance on Thursday.

The River Falls School District says she was fired in 2008 because there were concerns about her relationships with students, staff and parents. The district says it had no knowledge of the alleged assault while O’Malley-Tietz was an employee.